The advent of small, mobile multipurpose devices such as smartphones and tablet or pad devices has resulted in a need for high-resolution, small form factor cameras for integration in the devices. Some small form factor cameras may incorporate an autofocus (AF) mechanism whereby the object focal distance can be adjusted to focus an object plane in front of the camera at an image plane to be captured by the image sensor. In some such autofocus mechanisms, the optical lens is moved as a single rigid body along the optical axis (referred to as the Z axis) of the camera to refocus the camera. Some cameras use a voice coil motor, which may include various combinations of magnets or motors to physically move the position of a camera lens, thereby adjusting the object focal distance of the lens.
Portable devices are often subjected to disturbances, such as dropping a device on the ground or bumping a device into another object. If an external impact causes a movable component, such as a camera lens, to collide with another internal component, damage may occur to one or both components. Moreover, the resultant rattling sound may not be aesthetically pleasing to a user. Thus, even if damage to a given component is minimal, the resultant sound of components colliding may be undesirable.
To prevent damage or rattling sounds from a mobile device, collisions between components must be avoided or minimized. However, actively preventing such collisions may rapidly deplete battery life. For example, constantly providing power to a voice coil motor may help to prevent a camera lens from moving and colliding due to an external disturbance, but much current will be consumed due to current draw. In such devices, the ability to avoid internal component collisions while minimizing power consumption is useful.